1. Field of the Invention
The present invention relates to the laying and maintaining of railways, and, more particularly, to a machine for automatically installing clips for securing rails to ties.
2. Description of the Related Art
Railroad track is composed of rail sections laid parallel and spaced apart a uniform distance or gauge. The rails rest upon beams called ties or sleepers typically made of wood or concrete. The ties are spaced at regular intervals beneath the rails and are embedded in rock ballast to form a continuous supporting guideway upon which trains travel.
Track laying was originally accomplished entirely by hand labor using very large track gangs. This was dangerous and labor intensive work, and much of the evolution in track construction has concerned easing labor and improving safety. Today, track construction is accomplished almost entirely by mechanized art capable of laying track at a very rapid rate.
It is critical that the track be maintained in the correct geometry. The proper gauge is especially important, since gauges which are too wide or narrow may result in a rough ride, excessive wear, or even derailment. Thus, the durability of the attachment of the rails to the ties is highly important.
Much effort has gone into the study of the best means of restraining rails at their true geometry. The earliest means was to drive spikes into wood ties until the protruding head of the spike bears against the toe of the rail. Such spikes are still in use. Another type of spike is threaded and screwed into the wood tie. Such spikes are subject to loosening under the constant working of heavy wheel loads, and such loosening allows the track geometry to vary. Also, the development and growing use of concrete ties has led away from the use of spikes.
Because of the inherent disadvantages in spikes and the use of concrete ties, a trend has developed towards resilient fastening of the rail. One fastening device in current wide use is a steel bar bent into the form of a spring clip. One such clip is the PANDROL "e" clip sold by Pandrol Incorporated of Bridgeport, N.J. As shown in FIG. 25, this clip 10 is a generally cylindrical rod bent into a shape having a first free end portion forming a toe 12, an outwardly and upwardly arching front arch 14, a heel 15, a forwardly curving rear arch 16, and a second free end portion forming a center leg 18 disposed generally between the toe 12 and the heel 15.
Installed clips in use with concrete ties are shown in FIG. 26. The tie T is formed as an elongated block of concrete in which are embedded two pairs of cast iron or steel anchors one pair of which is shown at 20a, 20b. The lower extent of the rail R is formed with laterally extending rail toes 22. A rail pad 24 is disposed between the underside of the rail and the upper surface of the tie. Preferably, the pad 24 is made of a non-conductive elastomer to carry the bearing load from the rail to the tie and to prevent train control electrical signals from being shunted to earth through the somewhat conductive tie.
On either side of the rail, the upper extent of each anchor 20a, 20b is formed as a shoulder 26 protruding above the upper surface of the tie. Each shoulder is formed with a longitudinally extending hole 28 into which is inserted the center leg 18 of a clip. The heel 15 of each clip rests upon a ledge 29 formed on the outer extent of the shoulder. The toe 12 of each clip is disposed inwardly over a rail toe 22. An insulator 30 is disposed between the rail toe 22 and the clip toe 12. Each of the components is appropriately dimensioned such that the clip toe 12 bears down against the insulator 30 with a very heavy spring force sufficient to secure the rail in place.
The clips 10 may be used with other types of well known ties and anchors. For example, plates formed with upwardly arching shoulders may be attached by spikes to wood ties. The clips engage the shoulders in the same manner described above. The rail clip applicator of the present invention may also be used with a wide variety of such ties and anchors.
In the past, the clips 10 have been installed manually by placing the center leg 18 into alignment with the shoulder hole 28 and by pounding the clip into the shoulder. The clips have also been installed by a semi-automated method in which the clips are manually delivered, aligned, and started into the shoulders and are driven in by mechanical pincer devices. Such methods requires manual operations and are, therefore, relatively slow and labor intensive.
When the clips are pounded or driven into place in the shoulders, great care must be taken not to drive the clips too far. Referring to FIG. 24, a gap 32 should be maintained between the inner radius of the clip rear arch 16 and the adjacent vertical surface 34 of the shoulder 26. Preferably, the gap should be approximately 3/8 inch. If this gap is not maintained, pounding or driving of the clip may damage or even shear off the shoulder. Also, the rear arch 16 may be deformed resulting in a stress rise which can cause fatigue and premature failure.
The clip described above has a nominal weight of 1.7 pounds. Four clips are applied at each tie, i.e., two per rail to tie attachment. A normal work day of present rail laying or tie replacement equipment can be at the rate of over 2,000 ties per day. This is equivalent to 8,000 clips, or seven tons of clips, at each worksite each day. The fully automated delivery and driving of this quantity of clips to precisely the correct positions in an economical, rapid and reliable manner is a heretofore unmet need.